title: Significance of catalase in peroxisomal fatty acyl-CoA beta-oxidation: NADH oxidation by acetoacetyl-CoA and H2O2.
abstract: To clarify the significance of catalase in peroxisomes, we have examined the effect of aminotriazole treatment of rats on the activity of beta-hydroxybutyryl-CoA dehydrogenase in liver peroxisomes. When the effect of H2O2 on the dehydrogenase activity was examined using an extract of liver peroxisomes from aminotriazole-treated rats, the acetoacetyl-CoA-dependent oxidation of NADH was found to increase considerably on the addition of dilute H2O2. Such an effect of H2O2 was not seen on the beta-hydroxybutyryl-CoA-dependent reduction of NAD nor with extracts from untreated animals. We then noticed that similar NADH oxidation was caused non-enzymatically by a mixture of acetoacetyl-CoA and H2O2. The oxidation was dependent on both acetoacetyl-CoA and H2O2, and was blocked by scavengers of oxyradicals such as ascorbate and ethanol. Degradation products formed during the reaction of acetoacetyl-CoA with H2O2 had no NADH oxidizing activity, indicating that effective oxidant(s) were generated during the reaction of H2O2 with acetoacetyl-CoA. No other fatty acyl-CoA so far examined nor acetoacetate could replace acetoacetyl-CoA in this reaction. Therefore, if H2O2 were to be accumulated in peroxisomes, it would decrease both NADH and acetoacetyl-CoA, thus affecting the fatty acyl-CoA beta-oxidation system. These results, together with our previous finding that peroxisomal thiolase was significantly inactivated by H2O2 [Hashimoto, F. & Hayashi, H. (1987) Biochim. Biophys. Acta 921, 142-150] suggest that the role of catalase in peroxisomes is at least in part to protect the fatty acyl-CoA beta-oxidation system from the deleterious action of H2O2.
authors.affiliation: Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Josai University, Saitama.
authors.forename: F
authors.initials: F
authors.lastname: Hashimoto
authors.forename: H
authors.initials: H
authors.lastname: Hayashi
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000105:Acetyl Coenzyme A / Q000378:metabolism*; D000214:Acyl Coenzyme A / Q000378:metabolism*; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D002374:Catalase / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology; D016166:Free Radical Scavengers; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008297:Male; D008830:Microbodies / Q000187:drug effects / Q000201:enzymology*; D009243:NAD / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D000214:Acyl Coenzyme A; D016166:Free Radical Scavengers; D009243:NAD; C010667:acetoacetyl CoA; D000431:Ethanol; D000105:Acetyl Coenzyme A; D006861:Hydrogen Peroxide; D015094:3-Hydroxyacyl CoA Dehydrogenases; D002374:Catalase; D001205:Ascorbic Acid